Abstract
This study quantifies the sensitivity of surface runoff to drought and climate change in the Diyala watershed shared between Iraq and Iran. This was achieved through a combined use of a wide range of changes in the amount of precipitation (a decline between 0% and −40%) and in the potential evapotranspiration rate (an increase between 0% and +30%). The Medbasin-monthly rainfall-runoff model (Medbasin-M) was used for runoff simulation. The model was calibrated for twelve hydrologic years (1962−1973), and the simulation results were validated with the observed annual runoff for nine water years (1974−1982). For the calibration period, the correlation coefficient (r), the root mean squared error (RMSE), the mean absolute error (MAE) and the index of agreement (IoA) were 0.893, 2.117, 1.733 and 0.852, respectively. The corresponding values for validation were 0.762, 1.250, 1.093 and 0.863, in this order. The Reconnaissance Drought Index (RDI) and the Streamflow Drought Index (SDI) were analysed using DrinC software. Three nomographs were introduced to quantify the projected reductions in the annual runoff and the anticipated RDI and SDI values, respectively. The proposed methodology offers a simple, powerful and generic approach for predicting the rate of change (%) in annual runoff under climate change scenarios.
Highlights
The sustainable management of water resources in transboundary river basins has become a continuous challenge for riparian states
Results indicate promising model outcomes during the calibration and validation stages. This emphasises that the model can be safely used for further analysis, such as running the synthetic climatic scenarios and determining the proportional change (%) in the mean annual runoff relative to the normal climatic condition
A simple, generic, powerful and novel approach was presented for predicting the proportional change
Summary
The sustainable management of water resources in transboundary river basins has become a continuous challenge for riparian states. Drought and climate change are likely to put considerable pressure on water resources management and augment the level of vulnerability, of the downstream countries in transboundary river basins. Climate alteration is anticipated to escalate the recurrence, strength and duration of drought episodes in some regions. Droughts are categorized as meteorological, hydrological, agricultural and socio-economic phenomena. Numerous drought indices have been introduced in the literature [2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18].
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